8 ounces uncooked spaghetti
1 jar basil pesto
2 tablespoons heavy cream
1 tablespoon salted butter
1/4 cup Parmesan cheese, grated
Cook the spaghetti according to the instructions on the box.
Drain the pasta before it reaches al dente, putting about a cup of the the cooking water into a glass measuring cup.
Put a saucepan on the heat, reduce the heat to medium, and add the jar of pesto.
Once the pesto begins to simmer slightly, add the cream and the butter and stir well.
Put the pot with the spaghetti back on the burner on low heat, and add the sauce.
Stir until all the pasta is well-coated in the pesto sauce. If the sauce is too thick, add a few tablespoons or so of the cooking water to loosen it up.
Sprinkle liberally with parmesan cheese, and add a bit more of the cooking water to melt the cheese if necessary.
Serve immediately.